Regulatory Interaction between the Cystic Fibrosis Transmembrane Conductance Regulator and HCO3- Salvage Mechanisms in Model Systems and the Mouse Pancreatic Duct

Wooin Ahn, Kyung Hwan Kim, Jin Ah Lee, Joo Young Kim, Joo Young Choi, Orson W. Moe, Sharon L. Milgram, Shmuel Muallem, Min Goo Lee

Research output: Contribution to journalArticle

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Abstract

The pancreatic duct expresses cystic fibrosis transmembrane conductance regulator (CFTR) and HCO3- secretory and salvage mechanisms in the luminal membrane. Although CFTR plays a prominent role in HCO3- secretion, the role of CFTR in HCO3 - salvage is not known. In the present work, we used molecular, biochemical, and functional approaches to study the regulatory interaction between CFTR and the HCO3- salvage mechanism Na +/H+ exchanger isoform 3 (NHE3) in heterologous expression systems and in the native pancreatic duct. We found that CFTR regulates NHE3 activity by both acute and chronic mechanisms. In the pancreatic duct, CFTR increases expression of NHE3 in the luminal membrane. Thus, luminal expression of NHE3 was reduced by 53% in ducts of homozygote ΔF508 mice. Accordingly, luminal Na+-dependent and HOE694-sensitive recovery from an acid load was reduced by 60% in ducts of ΔF508 mice. CFTR and NHE3 were coimmunoprecipitated from PS120 cells expressing both proteins and the pancreatic duct of wild type mice but not from PS120 cells lacking CFTR or the pancreas of ΔF508 mice. The interaction between CFTR and NHE3 required the COOH-terminal PDZ binding motif of CFTR, and mutant CFTR proteins lacking the C terminus were not co-immunoprecipitated with NHE3. Furthermore, when expressed in PS120 cells, wild type CFTR, but not CFTR mutants lacking the C-terminal PDZ binding motif, augmented cAMP-dependent inhibition of NHE3 activity by 31%. These findings reveal that CFTR controls overall HCO 3- homeostasis by regulating both pancreatic ductal HCO3- secretory and salvage mechanisms.

Original languageEnglish (US)
Pages (from-to)17236-17243
Number of pages8
JournalJournal of Biological Chemistry
Volume276
Issue number20
DOIs
StatePublished - May 18 2001

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Salvaging
Cystic Fibrosis Transmembrane Conductance Regulator
Pancreatic Ducts
Ducts
Sodium-Hydrogen Antiporter
Protein Isoforms
Membranes
Homozygote
Protein C

ASJC Scopus subject areas

  • Biochemistry

Cite this

Regulatory Interaction between the Cystic Fibrosis Transmembrane Conductance Regulator and HCO3- Salvage Mechanisms in Model Systems and the Mouse Pancreatic Duct. / Ahn, Wooin; Kim, Kyung Hwan; Lee, Jin Ah; Kim, Joo Young; Choi, Joo Young; Moe, Orson W.; Milgram, Sharon L.; Muallem, Shmuel; Lee, Min Goo.

In: Journal of Biological Chemistry, Vol. 276, No. 20, 18.05.2001, p. 17236-17243.

Research output: Contribution to journalArticle

Ahn, Wooin ; Kim, Kyung Hwan ; Lee, Jin Ah ; Kim, Joo Young ; Choi, Joo Young ; Moe, Orson W. ; Milgram, Sharon L. ; Muallem, Shmuel ; Lee, Min Goo. / Regulatory Interaction between the Cystic Fibrosis Transmembrane Conductance Regulator and HCO3- Salvage Mechanisms in Model Systems and the Mouse Pancreatic Duct. In: Journal of Biological Chemistry. 2001 ; Vol. 276, No. 20. pp. 17236-17243.
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abstract = "The pancreatic duct expresses cystic fibrosis transmembrane conductance regulator (CFTR) and HCO3- secretory and salvage mechanisms in the luminal membrane. Although CFTR plays a prominent role in HCO3- secretion, the role of CFTR in HCO3 - salvage is not known. In the present work, we used molecular, biochemical, and functional approaches to study the regulatory interaction between CFTR and the HCO3- salvage mechanism Na +/H+ exchanger isoform 3 (NHE3) in heterologous expression systems and in the native pancreatic duct. We found that CFTR regulates NHE3 activity by both acute and chronic mechanisms. In the pancreatic duct, CFTR increases expression of NHE3 in the luminal membrane. Thus, luminal expression of NHE3 was reduced by 53{\%} in ducts of homozygote ΔF508 mice. Accordingly, luminal Na+-dependent and HOE694-sensitive recovery from an acid load was reduced by 60{\%} in ducts of ΔF508 mice. CFTR and NHE3 were coimmunoprecipitated from PS120 cells expressing both proteins and the pancreatic duct of wild type mice but not from PS120 cells lacking CFTR or the pancreas of ΔF508 mice. The interaction between CFTR and NHE3 required the COOH-terminal PDZ binding motif of CFTR, and mutant CFTR proteins lacking the C terminus were not co-immunoprecipitated with NHE3. Furthermore, when expressed in PS120 cells, wild type CFTR, but not CFTR mutants lacking the C-terminal PDZ binding motif, augmented cAMP-dependent inhibition of NHE3 activity by 31{\%}. These findings reveal that CFTR controls overall HCO 3- homeostasis by regulating both pancreatic ductal HCO3- secretory and salvage mechanisms.",
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T1 - Regulatory Interaction between the Cystic Fibrosis Transmembrane Conductance Regulator and HCO3- Salvage Mechanisms in Model Systems and the Mouse Pancreatic Duct

AU - Ahn, Wooin

AU - Kim, Kyung Hwan

AU - Lee, Jin Ah

AU - Kim, Joo Young

AU - Choi, Joo Young

AU - Moe, Orson W.

AU - Milgram, Sharon L.

AU - Muallem, Shmuel

AU - Lee, Min Goo

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N2 - The pancreatic duct expresses cystic fibrosis transmembrane conductance regulator (CFTR) and HCO3- secretory and salvage mechanisms in the luminal membrane. Although CFTR plays a prominent role in HCO3- secretion, the role of CFTR in HCO3 - salvage is not known. In the present work, we used molecular, biochemical, and functional approaches to study the regulatory interaction between CFTR and the HCO3- salvage mechanism Na +/H+ exchanger isoform 3 (NHE3) in heterologous expression systems and in the native pancreatic duct. We found that CFTR regulates NHE3 activity by both acute and chronic mechanisms. In the pancreatic duct, CFTR increases expression of NHE3 in the luminal membrane. Thus, luminal expression of NHE3 was reduced by 53% in ducts of homozygote ΔF508 mice. Accordingly, luminal Na+-dependent and HOE694-sensitive recovery from an acid load was reduced by 60% in ducts of ΔF508 mice. CFTR and NHE3 were coimmunoprecipitated from PS120 cells expressing both proteins and the pancreatic duct of wild type mice but not from PS120 cells lacking CFTR or the pancreas of ΔF508 mice. The interaction between CFTR and NHE3 required the COOH-terminal PDZ binding motif of CFTR, and mutant CFTR proteins lacking the C terminus were not co-immunoprecipitated with NHE3. Furthermore, when expressed in PS120 cells, wild type CFTR, but not CFTR mutants lacking the C-terminal PDZ binding motif, augmented cAMP-dependent inhibition of NHE3 activity by 31%. These findings reveal that CFTR controls overall HCO 3- homeostasis by regulating both pancreatic ductal HCO3- secretory and salvage mechanisms.

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